![]() Ideally, the rider should be X-rayed when standing and wearing properly adjusted riding shoes (including cleat wedges where appropriate) and the measurement taken from the washers around the screws locking the cleats to the shoe, to the top of the ball and socket hip joint.”Ī Functional Leg Length Difference (FLLD) occurs when there are functional factors that effectively lessen the ability of one leg to reach as far towards the bottom of the pedal stroke as the other leg. If a patient simply stands barefoot and gets X-rays taken, the eversion and foot posture that will almost certainly exist (as well as the impact of other postural issues) will distort the result and give a non-functional measurement. The measurement must be of functional leg length. It can’t be done with a tape measure, and measurement of leg length on X-ray is much better. ![]() “The accurate measurement of leg length is amazingly difficult. I’ve taken the liberty of copying it here: Bernard, apart from being a knowledgeable bloke and Professor of Medicine, is a bike nut like the rest of us. The best protocol I’ve seen for imaging to determine relative leg length was given to me by Bernard Pearn-Rowe. The X-ray is accurate as long as both legs are in the same plane. An X-ray is a 2 dimensional image and as something like 96% of people display a lateral pelvic tilt (my fitting clients over some years) which causes them to stand with one knee more locked than the other in normal standing posture, this means that the leg with the greater bend at the knee when the image is taken is ‘effectively’ shorter in a 2 dimensional sense, than it is with leg extended, leading to inaccuracy. Many X-rays or scans for leg length are not definitive in terms of accurately determining LLD unless taken with knees locked out and the subject standing as tall as they can. Better still, because it is definitive, is an X-ray, scan or MRI which will give certainty as to any difference in leg length providing it is taken properly. This is commonly determined by observation and external measurement, though this method, even when competently performed, still has an error factor of plus / minus 5mm. The shim stack comprises 1 x 3mm shim and 2 x 2mm shims.Ī Measurable Leg Length Difference (MLLD) occurs when there is a measurable difference in the length of one or more bones in one leg relative to the other. ![]() ![]() For instance, below is a pic of a 7mm shim stack underneath a Look Keo cleat. We manufacture each shim type in 2mm and 3mm and thicknesses so as to allow a shim stack of any height from 2mm upwards in single mm increments. Shimano SPD-SL / Look Delta compatibleĪnd, on the bottom row from left to right: From left to right on top row they are:Ģ. A shim stack may be needed as a short term, medium term or permanent fixture. A shim is a means to lengthen a functionally or measurably short leg while cycling. ![]()
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